Quelle  spi-slave-system-control.c   Sprache: C

/*
 * SPI slave handler controlling system state
 *
 * This SPI slave handler allows remote control of system reboot, power off,
 * halt, and suspend.
 *
 * Copyright (C) 2016-2017 Glider bvba
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Usage (assuming /dev/spidev2.0 corresponds to the SPI master on the remote
 * system):
 *
 *   # reboot='\x7c\x50'
 *   # poweroff='\x71\x3f'
 *   # halt='\x38\x76'
 *   # suspend='\x1b\x1b'
 *   # spidev_test -D /dev/spidev2.0 -p $suspend # or $reboot, $poweroff, $halt
 */

#include <linux/completion.h>
#include <linux/module.h>
#include <linux/reboot.h>
#include <linux/suspend.h>
#include <linux/spi/spi.h>

/*
 * The numbers are chosen to display something human-readable on two 7-segment
 * displays connected to two 74HC595 shift registers
 */
#define CMD_REBOOT 0x7c50 /* rb */
#define CMD_POWEROFF 0x713f /* OF */
#define CMD_HALT 0x3876 /* HL */
#define CMD_SUSPEND 0x1b1b /* ZZ */

struct spi_slave_system_control_priv {
 struct spi_device *spi;
 struct completion finished;
 struct spi_transfer xfer;
 struct spi_message msg;
 __be16 cmd;
};

static
int spi_slave_system_control_submit(struct spi_slave_system_control_priv *priv);

static void spi_slave_system_control_complete(void *arg)
{
 struct spi_slave_system_control_priv *priv = arg;
 u16 cmd;
 int ret;

 if (priv->msg.status)
  goto terminate;

 cmd = be16_to_cpu(priv->cmd);
 switch (cmd) {
 case CMD_REBOOT:
  dev_info(&priv->spi->dev, "Rebooting system...\n");
  kernel_restart(NULL);
  break;

 case CMD_POWEROFF:
  dev_info(&priv->spi->dev, "Powering off system...\n");
  kernel_power_off();
  break;

 case CMD_HALT:
  dev_info(&priv->spi->dev, "Halting system...\n");
  kernel_halt();
  break;

 case CMD_SUSPEND:
  dev_info(&priv->spi->dev, "Suspending system...\n");
  pm_suspend(PM_SUSPEND_MEM);
  break;

 default:
  dev_warn(&priv->spi->dev, "Unknown command 0x%x\n", cmd);
  break;
 }

 ret = spi_slave_system_control_submit(priv);
 if (ret)
  goto terminate;

 return;

terminate:
 dev_info(&priv->spi->dev, "Terminating\n");
 complete(&priv->finished);
}

static
int spi_slave_system_control_submit(struct spi_slave_system_control_priv *priv)
{
 int ret;

 spi_message_init_with_transfers(&priv->msg, &priv->xfer, 1);

 priv->msg.complete = spi_slave_system_control_complete;
 priv->msg.context = priv;

 ret = spi_async(priv->spi, &priv->msg);
 if (ret)
  dev_err(&priv->spi->dev, "spi_async() failed %d\n", ret);

 return ret;
}

static int spi_slave_system_control_probe(struct spi_device *spi)
{
 struct spi_slave_system_control_priv *priv;
 int ret;

 priv = devm_kzalloc(&spi->dev, sizeof(*priv), GFP_KERNEL);
 if (!priv)
  return -ENOMEM;

 priv->spi = spi;
 init_completion(&priv->finished);
 priv->xfer.rx_buf = &priv->cmd;
 priv->xfer.len = sizeof(priv->cmd);

 ret = spi_slave_system_control_submit(priv);
 if (ret)
  return ret;

 spi_set_drvdata(spi, priv);
 return 0;
}

static void spi_slave_system_control_remove(struct spi_device *spi)
{
 struct spi_slave_system_control_priv *priv = spi_get_drvdata(spi);

 spi_target_abort(spi);
 wait_for_completion(&priv->finished);
}

static struct spi_driver spi_slave_system_control_driver = {
 .driver = {
  .name = "spi-slave-system-control",
 },
 .probe  = spi_slave_system_control_probe,
 .remove  = spi_slave_system_control_remove,
};
module_spi_driver(spi_slave_system_control_driver);

MODULE_AUTHOR("Geert Uytterhoeven ");
MODULE_DESCRIPTION("SPI slave handler controlling system state");
MODULE_LICENSE("GPL v2");